The present invention relates to a vehicular lamp unit, and a manufacturing method therefor, in which a front lens and a lamp body are directly bonded together.
Conventionally, two types of methods for bonding a front lens and a lamp body of a vehicular lamp unit have been well known, that is, indirect bonding via a seal member (for example, the hot melt sealing method), and direct bonding by bringing the two members into direct abutment (for example, heating plate welding, vibration welding, ultrasonic bonding, or the like).
As a direct bonding method, laser beam welding has been well known in other technical fields. Such a method is applicable to the bonding of a front lens and a lamp body. One such a process will be described with reference to FIG. 8 (see also commonly assigned co-pending U.S. patent application Ser. No. 09/548,361).
Referring to FIG. 8, a seal leg 2a extending in the outward direction along the outer periphery of a front lens 2 is formed. A receiving surface 4a is formed along the opening portion of the front end of a lamp body 4. The lamp body 4 is placed on a receiving jig 102. The front lens 2 is set onto the lamp body 4 in such a manner that an end surface 2b of the seal leg 2a is brought into abutment against the receiving surface 4a. The front lens 2 is further covered with a transparent pressure plate 104 through which the front lens 2 is pressed to the lamp body 4. In the above state, a laser beam L is irradiated onto the receiving surface 4a from a position upward of the front lens 2 through the transparent pressure plate 104 and the seal leg 2a. As a result, the receiving surface 4a. is heated and melted by the irradiation energy of the laser beam L so as to fuse with the end surface 2b of the seal leg 2a that has been melted by the heat. The front lens 2 and the lamp body 4 thus are bonded together by scanning the laser beam L along the seal leg 2a over the entire length of the front lens 2.
Employing the above-described laser beam welding method allows bonding of the front lens 2 and the lamp body 4 without generating burrs on the respective bonded surfaces, resulting in improved quality of the outer appearance around the peripheral portion of the bonded surfaces. However, this welding method may result in certain disadvantages.
Namely, in the laser beam welding method, the laser beam L is irradiated by permeating through the transparent pressure plate 104 and the seal leg 2a, which reduces the irradiation energy of the laser beam L by an amount proportional to the permeation distance (the distance obtained by adding the entire length Do of the seal leg 2a to the thickness of the transparent pressure plate 104). Moreover, the front lens 2 has to be pressed at a point displaced from the position just above the seal leg 2a because the optical path of the laser beam L must be avoided. Accordingly, the end surface 2b of the seal leg 2a and the receiving surface 4a cannot be brought into abutment with a uniform pressure in the width direction. As a result, the required bonding strength cannot be ensured over the entire width of the bonded surface.
The invention has been made in view of the foregoing circumstances. It is therefore an object of the invention to provide a vehicular lamp unit and a manufacturing method therefor in which the front lens and the lamp body are directly bonded together so as to improve the outer appearance quality as well as to enhance the strength of bonding between the front lens and the lamp body.
The aforementioned object is realized by the invention by employing laser beam welding as the method for bonding the front lens and the lamp body together and by suitably establishing the configuration of the peripheral portion of the bonded surfaces.
The vehicular lamp unit of the invention having a front lens and a lamp body directly bonded together is characterized in that a seal leg extending in an outward direction is formed on the outer periphery of the front lens, a receiving surface that is brought into abutment against an end surface of the seal leg is formed on the lamp body, the end surface of the seal leg and the receiving surface are directly bonded together through laser beam welding, and a laser beam receiving surface, which protrudes to direct a laser beam entering from a direction at an angle with respect to the reference axis of the lamp to the end surface, is formed on an outer side surface of the seal leg.
The term xe2x80x9claser beam weldingxe2x80x9d indicates a bonding method wherein a laser beam transmitting member that allows permeation of the laser beam is brought into abutment against a laser beam non-transmitting member that does not allow permeation of the laser beam, both members are pressed in the outward direction, and a laser beam is irradiated onto the abutment surfaces of the two members through the laser beam transmission member so as to heat the laser beam non-transmission member. As a result, both members are fused together. The laser beam used for the laser beam welding is not particularly limited, and, for example, a semiconductor laser, a YAG laser or the like may be employed.
The material for forming the lamp body is not particularly limited so long as it does not allow transmission of the laser beam and is heated and melted by the laser beam irradiation. For efficient laser beam welding, it is preferable that the lamp body is formed of a black-colored material to which an auxiliary material such as carbon black has been added so as to enhance the laser beam absorbing capability of the lamp body.
Also, the material for the front lens is not particularly limited so long as it allows transmission of visible light and the laser beam and it can be fused and fixed to a lamp body that has been melted.
The configuration of the laser beam receiving surface also is not particularly limited so long as it is capable of leading the laser beam irradiated from a direction at an angle with respect to the bonded surface to the end surface of the seal leg.
In the aforementioned construction, the front lens and the lamp body of the vehicular lamp unit of the invention are directly bonded together by laser beam welding such that the end surface of the seal leg formed on the front lens is bonded to the receiving surface formed on the lamp body. This allows bonding without generating burrs on the respective bonded surfaces, thus improving the appearance quality around the bonded surfaces.
The vehicular lamp unit of the invention has a projecting laser beam receiving surface for directing the laser beam irradiated onto the outer surface of the seal leg that extends in the outward direction from a direction at an angle with respect to the bonded surface to the end surface of the seal leg. This provides the advantageous effects described below.
During the bonding operation, the permeation distance of the laser beam corresponds to the distance from the laser beam receiving surface of the seal leg to the end surface. This distance can be made much shorter than in the case where bonding is performed by laser beam permeation through a transparent pressure plate and the seal leg. As a result, the laser beam bonding can be performed with sufficient irradiation energy.
The laser beam is irradiated from a direction at an angle with respect to the bonded surface. This makes it possible to press the front lens by applying pressure to the base end portion of the seal leg. The end surface of the seal leg portion and the receiving surface can be abutted with one another under uniform pressure relative to the width direction thereof. The required bonding strength thus can be easily achieved across the entire width of the bonded surface.
In the vehicular lamp unit having the front lens and the lamp body directly bonded together according to the present invention, the bonding strength between the front lens and the lamp body is sufficiently enhanced while improving the outer appearance quality of the portion around the bonded surfaces.
With the vehicular lamp unit constructed such that the end portion of the seal leg is bent toward the outer periphery at a predetermined angle with respect to the bonded surface, the advantageous effects described below can be obtained.
Even in a case where the end surface of the seal leg or the receiving surface has a wave-like irregularity owing to insufficient smoothness such that gaps are created in areas therebetween, the pressure acting on the members to be bonded causes slippage between them because the bonded surface is inclined. This slippage serves to seal the gaps created in areas between the two members so as to enable abutment thereof over the entire length of the bonded surface. Accordingly, bonding failure is prevented. The bending angle of the end portion is not limited to a particular value, whether large or small, so long as it is less than 90xc2x0.
In this case, the receiving surface of the lamp body may be provided with an outer rib that projects in the outward direction along the outer side surface of the end portion of the seal leg of the front lens such that the outer rib is brought into abutment against the seal leg. This makes it possible to prevent generation of unnecessary slippage between the end surface of the seal leg and the receiving surface owing to the pressure acting on the bonded surface during the bonding operation.
In the above case, the receiving surface of the lamp body may further be provided with an inner rib that projects in the outward direction along the inner side surface of the end portion of the seal leg of the front lens. Even if the direction of a laser beam irradiated from a direction substantially orthogonal to the end surface of the seal leg is slightly displaced, the laser beam can still be irradiated onto the outer side surface of the inner rib so as to properly heat and melt the inner rib. The outer side surface of the inner rib and the inner side surface of the seal leg can be bonded to define a second bonded surface. This makes it possible to further enhance the bonding strength between the front lens and the lamp body.